Papers by Keyword: Microindentation Fracture Toughness

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Authors: N. López-Perrusquia, Ivan Campos-Silva, José Martínez-Trinidad, A. Avilés, E. Alvárez-Castañeda, S. Juárez-Torres
Abstract: The fracture toughness of AISI H13 borided steel and the strength adhesion of the coated system were estimated in the present work. The formation of the layers was carried out by the powder pack boriding process at 1273 K with 8 h of treatment. The fracture toughness (KC) of the layer is estimated at 25 and 45 m from the surface using four different Vickers indentation loads. The KC values were estimated by the extension of Palmqvist cracks parallel and perpendicular to the surface obtained at the indentation corners. The adherence of the layer/substrate was evaluated in qualitative form through the Rockwell-C indentation technique. The results obtained by both techniques, show, in first instance, that the fracture toughness of the boride layer can be expressed in the form (KC) (π/2) > (KC) > (KC) (0). Also, high delamination is obtained around the Rockwell-C indentation prints that denote poor adhesion in the coating-substrate interface.
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Authors: T. Nejatian, A. Johnson, R. Van Noort
Abstract: The fracture resistance of polymethyl methacrylate (PMMA) the most popular denture base materials, is not satisfactory. The aim of this study is to improve the mechanical properties of PMMA by adding filler particles. Different inorganic filler particles including micronised glass flakes, acryl silane micronised, glass flakes 350nm, TiO2 and ZrO2 with different ratios by weight were incorporated into heat-cure plain PMMA and processed with optimal condition [2.5:1 Powder/ monomer ratio, conventional packing method and water bath curing for 2 hours at 95°C] to produce 12mm diameter and 2mm thick discs. Plain PMMA without additives was prepared as a test control. Three types of mechanical tests, biaxial flexure, microindentation fracture toughness and Vickers hardness were carried out on the samples. It was found that incorporating the particles did not improve the biaxial flexural strength of the resin. However, TiO2, ZrO2 and micronised glass flakes increased the fracture toughness of the resin. The hardness of PMMA was improved by the incorporation of all the particles.
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